Methods and apparatus to test a subscriber line for a broadband access service

ABSTRACT

Methods and apparatus to test a subscriber line for a broadband access service are disclosed. An example network interface device (NID) comprises a tone generator to transmit a tone on a subscriber line to characterize the subscriber line while a DSL modem is providing a DSL service via the subscriber line, the tone having a frequency occurring within a range of frequencies in use by the DSL modem to provide the DSL service, and a pair of terminals to couple the DSL modem and the tone generator to the subscriber line.

FIELD OF THE DISCLOSURE

This disclosure relates generally to broadband access services and/orsystems and, more particularly, to methods and apparatus to test asubscriber line for a broadband access service.

BACKGROUND

Communication systems using digital subscriber line (DSL) technologiesand/or passive optical network (PON) technologies are commonly utilizedto provide Internet related services to subscribers, such as, forexample, homes and/or businesses (also referred to herein as users,customers and/or customer-premises). PON technologies enable a serviceprovider to efficiently provide a high data-rate broadband Internetnetwork, broadband service and/or broadband content via fiber opticcables. DSL technologies enable customers to utilize telephone lines(e.g., ordinary twisted-pair copper telephone lines used to providePlain Old Telephone System (POTS) services) to connect the customer to,for example, a high data-rate broadband Internet network, broadbandservice and/or broadband content. For example, a communication companyand/or service provider may utilize a plurality of modems (e.g., aplurality of DSL modems) implemented by a DSL Access Multiplexer (DSLAM)at a central office (CO) to provide DSL communication services to aplurality of modems located at respective customer-premises. In general,a CO DSL modem receives broadband service content from, for example, abackbone server and forms a digital downstream DSL signal to betransmitted to a customer-premises DSL modem. Likewise, the centraloffice DSL modem receives an upstream DSL signal from thecustomer-premises DSL modem and provides the data transported in theupstream DSL signal to the backbone server.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example digital subscriber line(DSL) communication system constructed in accordance with the teachingsof the invention.

FIG. 2 illustrates example transmissions of tones by any or all of theexample tone generators of FIGS. 1, 4 and/or 5.

FIG. 3 illustrates an example modulation of a tone to provide anidentifier.

FIG. 4 illustrates an example manner of implementing the example networkinterface device (NID) of FIG. 1.

FIG. 5 illustrates an example manner of implementing a network interfacedevice for a passive optical network (PON).

FIG. 6 illustrates an example manner of implementing any or all of theexample tone generators of FIGS. 1, 4 and/or 5.

FIG. 7 illustrates an example manner of implementing any or all of theexample loop testers of FIG. 1.

FIG. 8 is a flowchart representative of an example process that may becarried out by, for example, a processor to implement any or all of theexample loop testers of FIGS. 1 and/or 7.

FIG. 9 is a schematic illustration of an example processor platform thatmay be used and/or programmed to execute the example machine accessibleinstructions of FIG. 8 to implement any or all of the example looptesters described herein.

DETAILED DESCRIPTION

Methods and apparatus to test a subscriber line for a broadband accessservice are disclosed. A disclosed example network interface device(NID) includes a tone generator to transmit a tone on a subscriber lineto characterize the subscriber line while a DSL modem is providing a DSLservice via the subscriber line, the tone having a frequency occurringwithin a range of frequencies in use by the DSL modem to provide the DSLservice, and a pair of terminals to couple the DSL modem and the tonegenerator to the subscriber line.

Another disclosed example network interface device (NID) includes a tonegenerator to generate a first optical signal, the first optical signalselected to identify the NID and having a wavelength occurring within arange of wavelengths in use by an optical network unit (ONU) coupled tothe NID, and an optical coupler to combine the first optical signal witha second optical signal generated by the ONU.

A disclosed example loop tester includes a power meter to measure apower of a tone received on a subscriber line, the tone having afrequency occurring within a range of frequencies in use by a digitalsubscriber line (DSL) modem to provide a DSL service via the subscriberline, and a loop length estimator to estimate a length of the subscriberline based on the measured power.

A disclosed example method to identify a subscriber loop includesreceiving a tone having a frequency occurring within a range offrequencies in use by a digital subscriber line (DSL) modem to provide aDSL service via the subscriber line, the tone transmitted by a tonegenerator located at a network interface device (NID), wherein the tonegenerator is distinct from the DSL modem, and demodulating the receivedtone to obtain a subscriber loop identifier.

In the interest of brevity and clarity, throughout the followingdisclosure references will be made to connecting a digital subscriberline (DSL) modem and/or a DSL communication service to a customerpremises, customer and/or subscriber. However, it will be readilyapparent to persons of ordinary skill in the art that connecting a DSLmodem to a customer premises, customer and/or subscriber involves, forexample, connecting a first DSL modem operated by a communicationscompany (e.g., a central office (CO) DSL modem implemented by a DSLaccess multiplexer (DSLAM)) to a second DSL modem located at, forexample, a customer-premises (e.g., a home and/or place of businessowned, leased and/or operated by a customer) via a twisted-pairtelephone line (i.e., a subscriber line). The customer-premises (e.g.,the second) DSL modem may be further connected to other communicationand/or computing devices (e.g., a personal computer, a set-top box,etc.) that the customer uses and/or operates to access a service (e.g.,Internet access, Internet protocol (IP) Television (TV), etc.) via theCO DSL modem, the customer-premises DSL modem, the subscriber line andthe communications company.

Moreover, while methods and apparatus to test a subscriber line for aDSL service and/or a passive optical network (PON) service are describedherein, persons of ordinary skill in the art will readily appreciatethat the example methods and apparatus may, additionally oralternatively, be used to test other wires and/or cables for othercommunication services. Other example wires and/or cables include, butare not limited to, those associated with public switched telephonenetwork (PSTN) systems, public land mobile network (PLMN) systems (e.g.,cellular), wireless distribution systems, wired or cable distributionsystems, coaxial cable distribution systems, Ultra High Frequency(UHF)/Very High Frequency (VHF) radio frequency systems, satellite orother extra-terrestrial systems, cellular distribution systems,power-line broadcast systems, fiber optic networks, and/or anycombination and/or hybrid of these devices, systems and/or networks.

FIG. 1 illustrates an example DSL communication system in which acentral office (CO) 105 provides data and/or communication services(e.g., telephone services, Internet services, data services, messagingservices, instant messaging services, electronic mail (email) services,chat services, video services, audio services, gaming services, etc.) toone or more customer-premises, one of which is designated at referencenumeral 110. To provide DSL communication services to thecustomer-premises 110, the example CO 105 of FIG. 1 includes any numberand/or type(s) of DSLAMs (one of which is designated at referencenumeral 115) and the example customer-premises 110 includes any type ofDSL modem 120. The example DSLAM 115 of FIG. 1 includes and/orimplements one or more CO DSL modems (not shown) for respective ones ofthe customer-premises locations. The example DSLAM 115, the CO DSLmodems comprising the DSLAM 115 and/or the example DSL modem 120 of FIG.1 may be implemented, for example, in accordance with the ITU-T G.993.xfamily of standards for very high-speed DSL (VDSL).

In the illustrated example of FIG. 1, the DSLAM 115 provides the DSLservice to the DSL modem 120 at the customer-premises 110 via asubscriber line 125. Subscriber lines are sometimes also referred to inthe industry as “wire-pairs” and/or “loops.” While throughout thisdisclosure reference is made to the example subscriber line 125 of FIG.1, persons of ordinary skill in the art will readily appreciate that asubscriber line (e.g., the example subscriber line 125) used to providea DSL service to a customer-premises location (e.g., the location 110)may include and/or be constructed from one or more segments oftwisted-pair telephone wire (e.g., a combination of a feeder one (F1)cable, a distribution cable, a drop cable, and/or customer-premiseswiring), terminals and/or distributions points (e.g., a serving areainterface (SAI), a serving terminal, a vault and/or a pedestal). Suchsegments of twisted-pair telephone wire may be spliced and/or connectedend-to-end, and/or may be connected at only one end thereby creating oneor more bridged-taps. Regardless of the number, type(s), gauge(s) and/ortopology of twisted-pair telephone wires used to construct the examplesubscriber line 125, it will be referred to herein in the singular formbut it will be understood that it may refer to one or more twisted-pairtelephone wire segments and may include one or more bridged taps.

As commonly used in the industry, the term “network demarcation point”denotes a location where cabling and/or equipment associated with aservice provider (e.g., associated with the CO 105 and/or the DSLAM 115)is physically, electrically and/or communicatively coupled to cablingand/or equipment associated with a customer-premises, a subscriber, auser and/or a customer (e.g., the example DSL modem 120). Suchsubscriber cabling and/or equipment is often owned by the customer butmay, in some instances, be owned, leased and/or otherwise provided bythe service provider. Typically a network demarcation unit (e.g., anetwork interface device (NID) 130) is located at the networkdemarcation point (e.g., on the outside of an exterior wall of thecustomer-premises 110) to implement the physical, electrical and/orcommunicative coupling between the subscriber and service provider sidesof the network demarcation point. The example NID 130 of FIG. 1 containsa first set of screw terminals, jacks and/or jumpers 135 to couple thesubscriber line 125 to the NID 130, and contains a second set of screwterminals, jacks and/or jumpers 140 to couple subscriber cabling 145 tothe NID 130. In such examples, a jumper and/or wire 142 couples the twosets of cabling 125 and 145 across the NID 130.

In some examples, to reduce and/or eliminate the effects of telephonewiring (not shown) within the customer-premises 110, the example DSLmodem 120 is located and/or implemented at and/or within the NID 130.However, the DSL modem 120 need not be implemented at and/or within theNID 130. For example, the DSL modem 120 could be implemented elsewherewithin the customer-premises 110. Alternatively, the DSL modem 120 maybe partially implemented within the NID 130. For example, a device(e.g., a POTS splitter) may be installed and/or implemented within theNID 130 to isolate the effects of telephone wiring and/or telephones(not shown) located in the customer-premises 110 from the DSL modem 120.

To facilitate testing of the example subscriber line 125, the exampleNID 130 of FIG. 1 includes a tone generator 150. The example tonegenerator (TG) 150 of FIG. 1 generates and transmits one or more signals(e.g., tones) on the subscriber line 125. The example tone generator 150transmits the signals while the DSL modem 120 is operating to provide aDSL service. An example manner of implementing any or all of the exampletone generators 150 of FIGS. 1 and/or 4 is described below in connectionwith FIG. 6.

As illustrated in FIG. 2, signal(s) 205, 206 and 207 generated by theexample tone generator 150 of FIG. 1 may have frequencies that occurwithin a range of frequencies 210 used (e.g., transmitted and/orreceived) by the example DSL modem 120 to provide a DSL service at thecustomer premises 110. The example tone generator 150 transmits thesignal(s) at power (e.g., signal) levels that provide for adequateand/or sufficiently accurate testing of the subscriber loop 125 whilereducing the impact on DSL services. For example as illustrated in FIG.2, the tone(s) generated by the example tone generator 150 aretransmitted with a signal power level of −60 dBm/Hz, whereas the DSLsignals 210 are transmitted with a nominal signal power level of −40dBm/Hz, thereby causing only 1 or 2 DSL sub-carriers (e.g., a modulated4.3125 thousand cycles per second (kHz) carrier of a DSL signal inaccordance with the Telecommunication Standardization Sector of theInternational Telecommunications Union (ITU-T) G.dmt standard) to bedisrupted by each of the example tone(s) 205-207.

In some examples, the signal(s) transmitted by the example tonegenerator 150 of FIG. 1 are encoded and/or modulated to facilitateidentification of the tone generator 150, the NID 130, the subscriberloop 125, the customer premises 110, and/or a subscriber associated withthe customer premises 110. For example as illustrated in FIG. 3, thesignal(s) (e.g., tone(s)) may be amplitude modulated, where theamplitude(s) of the signal(s) during different time periods depend uponan identifier associated with a particular tone generator 150, aparticular NID 130, a particular subscriber loop 125, a particularcustomer premises 110 and/or a particular subscriber. In the illustratedexample of FIG. 3 an identifier comprising a bit sequence {1 0 1 0 1 0 01} is being transmitted. During a first time period 305 corresponding tothe first bit of the sequence having a value of one (1), the signal istransmitted with an amplitude of one. During a second time period 310corresponding to the second bit of the sequence having a value of zero(0), the signal is transmitted with an amplitude of zero (e.g., nothingis transmitted). Additionally or alternatively, the signal(s) may bemodulated using phase modulation and/or code-division multiple-access(CDMA) modulation.

Turning to FIG. 4, signals generated and/or transmitted by the exampletone generator 150 of FIG. 1 may be coupled to the subscriber line 125via a coupling circuit and/or device, such as a balun 405. The examplebalun 405 of FIG. 4 is a passive circuit and/or component that matchesimpedances between two signals, and/or converts the unbalanced output410 (e.g., a signal transported on a single conductor and a ground) ofthe tone generator 150 into a balanced signal 415 (e.g., a signaltransported on two conductors and/or wires, with equal currents flowingin opposite directions) that may be coupled to the pair of terminals 135without causing appreciable effects to existing and/or ongoing DSLand/or telephone services. An example balun 405 is Model No. 0707LB fromNorth Hills™ Signal Processing, which converts between a 50 ohm (Ω)impedance unbalanced signal 410 and a 600Ω impedance balanced signal 415suitable for coupling onto a twisted-pair telephone line. Additionallyor alternatively, the signals 410 generated and/or transmitted by thetone generator 150 may be coupled directly to the pair of terminals 135without use of an intervening coupling circuit and/or device. Theexample tone generator 150 and/or the example balun 405 may beimplemented, included and/or operated at the NID 130 even when nocustomer wiring 145 and/or customer premises devices (e.g., the DSLmodem 120 and/or a telephone) are coupled to the NID 130.

Returning to FIG. 1, to test the example subscriber line 125 usingsignals transmitted by the example tone generator 150, the example DSLcommunication system of FIG. 1 includes one or more loop testers, two ofwhich are designated at reference numerals 155 and 160. The example looptesters 155 and 160 of FIG. 1 may be battery-operated, portable and/orhandheld devices useable by a technician, installer and/or serviceperson to test the subscriber line 125, and may be used a) outsideand/or within the customer-premises 110, b) outside and/or within the CO105, and/or c) anywhere along the subscriber loop 125 (e.g., at a wiringcabinet and/or wiring pedestal). Additionally or alternatively, theexample loop testers 155 and/or 160 of FIG. 1 may be a substantiallyfixed-location devices implemented within the CO 105 (e.g., implementedwithin a rack of equipment) and operable and/or configurable to test thesubscriber loop 125 and/or any number of additional or alternativesubscriber loops (not shown). In such instances, the example loop tester155, 160 may be coupled to the subscriber loop 125 via a switch 165(e.g., a switch manufactured by Spirent® Communications), which isconfigurable to connect, at any particular time, any one of a pluralityof subscriber loops (e.g., the example subscriber loop 125) to theexample loop tester 160. An example manner of implementing any or all ofthe example loop testers 155 and 160 of FIG. 1 is described below inconnection with FIG. 6.

The example loop testers 155 and 160 of FIG. 1 measure the power atwhich signals transmitted by the example tone generator 150 are receivedat the loop tester 155, 160. For example, the loop tester(s) 155 and/or160 may measure the attenuation of one or more of the tones transmittedby the tone generator 150. The example loop tester(s) 155 and/or 160then uses the measured attenuation(s) to estimate the loop loss of thesubscriber loop 125 and/or to estimate the length of the subscriber loop125. For example, using a database (e.g., table) that associates, for aparticular frequency, signal attenuation values with loop lengths, theloop tester(s) 155 and/or 160 can determine (e.g., estimate) a length ofthe subscriber line 125. If more than one signal attenuation value(e.g., at more than one of the example frequencies 205-207 of FIG. 2) ismeasured, the loop testers 155 and 160 can estimate a loop length basedon each of the signal attenuations, and then average the estimated looplengths to obtain a single estimated loop length. Other methods andapparatus to estimate loop lengths given one or more signal attenuationvalues are described in U.S. patent application Ser. No. 11/751,353,filed on May 21, 2007, and entitled “Methods and Apparatus toCharacterize a Digital Subscriber Line (DSL) Subscriber Loop.” U.S.patent application Ser. No. 11/751,353 is hereby incorporated byreference in its entirety.

To store data and/or information associated with subscriber lines, theexample DSL communication system of FIG. 1 includes a loop database 170.The example loop database 170 of FIG. 1 stores a plurality of databaserecords for respective ones of a plurality of subscriber lines (e.g.,the example subscriber line 125). Example information that may be storedin a database record includes, but is not limited to, an estimated looplength, DSL connection rate, error rates, signal attenuation,signal-to-noise ratios, bit allocations, DSL modem configuration, etc.When the example loop tester(s) 155 and/or 160 of FIG. 1 estimate a looplength for a subscriber line, they may update the corresponding databaserecord in the loop database 170. Such updates may occur when theestimation is performed, and/or may be stored by and/or within the looptester 155, 160 and then used to update the loop database 170 at a latertime. Although this disclosure references multiple loop testers 155 and160, the measurements and/or estimations discussed herein may beaccomplished with one or more loop testers.

FIG. 5 illustrates an example manner of implementing a NID 505 for aPON. The example NID 505 of FIG. 5 optically couples optical signalsbetween a PON subscriber line 510 and a customer premises optical cable515. The example customer premises optical cable 515 may be, forexample, coupled to an optical network unit (ONU) 520 located within acustomer premises (not shown).

To facilitate testing of the example PON subscriber line 510 and/or tofacilitate identification of the NID 505, the example ONU 520, asubscriber, and/or a customer premises, the example NID 505 of FIG. 5includes the example tone generator 525, an electrical-to-opticalconverter 530 and an optical coupler 535. The example tone generator 525of FIG. 5 generates and transmits one or more optical signals (e.g.,tones) on the PON subscriber line 510. The example tone generator 525transmits the signals while the ONU 520 is operating. As described abovein connection with FIG. 2, the example tone generator 525 transmitsoptical signals 205-207 falling within a range of optical wavelengths210 in use by the example ONU 520. Moreover as described above inconnection with FIG. 3, the optical signal(s) transmitted by the exampletone generator 525 may be modulated (e.g., amplitude modulated, phasemodulated, CDMA modulated and/or otherwise) to convey one or moreidentifiers associated with the example NID 505, the example ONU 520, asubscriber, and/or a customer premises. An example manner ofimplementing the example tone generator 525 of FIG. 5 is described belowin connection with FIG. 6.

FIG. 6 illustrates an example manner of implementing any or all of theexample tone generators 150 and/or 525 of FIGS. 1, 4 and/or 5. While anyor all of the example tone generators 150 and/or 525 may be representedby the device of FIG. 6, for ease of discussion, the example device ofFIG. 6 is referred to as tone generator 150. To generate one or moretones, the example tone generator 150 of FIG. 6 includes a signalgenerator 605. Using any type(s) and/or numbers of device, circuits,logic, method(s) and/or algorithm(s), the example signal generator 605of FIG. 6 generates one or more tones. How many and/or the frequenciesof the generated tones generated by the example signal generator 605 arepre-configured and/or built into the example tone generation module 605.However, the generation of tones by the example signal generator 605 maybe programmable and/or configurable.

To modulate signals, the example tone generator 150 of FIG. 6 includes amodulator 610 and an identifier 615. Using any modulation technique(e.g., amplitude, phase, CDMA and/or otherwise), circuit(s), logic,devices and/or algorithm(s), the example modulator 610 modulates one ormore of the tones generated by the example signal generator 605. Anexample modulation that may be implemented by the example modulator 610is described above in connection with FIG. 3.

While an example manner of implementing any or all of the example tonegenerators 150 and/or 525 of FIGS. 1, 4 and/or 5 has been illustrated inFIG. 6, one or more of the elements, processes and/or devicesillustrated in FIG. 6 may be combined, divided, re-arranged, omitted,eliminated and/or implemented in any other way. Further, the examplesignal generator 605, the example modulator 610 and/or, more generally,the example tone generator 150 of FIG. 6 may be implemented by hardware,software, firmware and/or any combination of hardware, software and/orfirmware. Further still, the example tone generator 150 of FIG. 6 mayinclude one or more elements, processes and/or devices in addition to,or instead of, those illustrated in FIG. 6, and/or may include more thanone of any or all of the illustrated elements, processes and devices.

FIG. 7 illustrates an example manner of implementing any or all of theexample loop testers 155 and 160 of FIG. 1. While either of the exampleloop testers 155 and 160 may be represented by the example device ofFIG. 7, for ease of discussion, the example device of FIG. 7 will bereferred to as loop tester 155. To direct the operations of the exampleloop tester 155 of FIG. 7, the loop tester 155 includes any type ofcontroller 705. The example controller 705 of FIG. 7 may be one or moreof any type of processors such as, for example, a microprocessor, amicrocontroller, a processor core, a digital signal processor (DSP), aDSP core, an advanced reduced instruction set computing (RISC) machine(ARM) processor, etc. The example controller 705 executes codedinstructions which may be present in a memory (not shown) of thecontroller 705 (e.g., within a random-access memory (RAM) and/or aread-only memory (ROM)) and/or within an on-board memory of thecontroller 705. For example, the example machine accessible instructionsof FIG. 8 may be executed by the controller 705 to direct the looptester 155 to test a subscriber line for a communication service.

To allow a person to operate the example loop tester 155 of FIG. 7, theloop tester 155 of FIG. 7 includes any number and/or type(s) ofinterfaces 715. In general, the example interface(s) 710 of FIG. 7 areused to initiate testing and/or identification of a subscriber line,and/or to obtain testing and/or identification results. Exampleinterface(s) 710 include, but are not limited to, any number ofbutton(s), key(s), keypad(s), screen(s), display(s), light emittingdiode(s), etc. Additionally or alternatively, the example interface 715of FIG. 7 may be implemented and/or provided by an operating systemexecuted by the example controller 705. For example, if a loop tester155 is implemented by, within and/or in conjunction with a portablecomputing device (e.g., a laptop and/or personal digital assistant), theinterfaces 710 may be implemented by the portable computing deviceand/or an operating system executing on the controller 705. If a looptester 155 is implemented within, for example, a rack of equipment, theexample interface(s) 715 may be an application programming interface(API) via which the loop tester 155 can be controlled by otherequipment. The example interface(s) 715 may, additionally oralternatively, be used to, for example, control the example switch 165of FIG. 1 to select a specific subscriber line to be coupled to the looptester 155.

To couple a received signal to the example loop tester 155 of FIG. 7,the example loop tester 155 includes a coupling circuit 715. Examplecoupling circuits 715 include, but are not limited to a balun, anantenna and/or an optical-to-electrical converter. A balun 715 may beused to electrically couple a twisted-wire pair subscriber line to theloop tester 155. An antenna 715 may be used to couple radio wavesemitted by a subscriber line to the loop tester 155. For example, theloop tester 155 may not be electrically or optically connected to agiven subscriber line, but instead may need only be near to a subscriberline to be tested and/or identified. An optical-to-electrical converter715 may be used to convert an optical signal on a PON to an electricalsignal and to couple the electrical signal to the loop tester 155.

To measure received signal power, the example loop tester 155 of FIG. 7includes a power meter 720. Using any number of circuit(s), device(s),logic, algorithm(s) and/or method(s), the example power meter 720measures the received signal power of one or more received signals(e.g., one or more received tones).

To estimate a loop length, the example loop tester 155 of FIG. 7includes a loop length estimator 725. The example loop length estimator725 of FIG. 1 uses received signal power values measured by the examplepower meter 720 to estimate the length of a subscriber loop (e.g., theexample subscriber loop 125 of FIG. 1). Knowing the transmitted signallevel of a tone (e.g., −20 dBm/Hz), the example loop length estimator725 can determine the attenuation of the tone. Then, for example, theloop length estimator 725 can use a database (e.g., table) thatassociates, for a particular frequency, signal attenuation values withloop lengths to determine (e.g., estimate) a length of the subscriberline. If more than one signal attenuation value is available (possiblyfor more than one frequency), the loop length estimator estimates a looplength based on each of the signal attenuations, and then averages theestimated loop lengths to obtain a single estimated loop length. Othermethods and apparatus to estimate loop lengths given one or more signalattenuation values are described in U.S. patent application Ser. No.11/751,353, filed on May 21, 2007, and entitled “Methods and Apparatusto Characterize a Digital Subscriber Line (DSL) Subscriber Loop.”

To identify a device, customer-premise and/or subscriber associated witha received signal, the example loop tester 155 of FIG. 7 includes a loopidentifier 730. The example loop identifier 730 demodulates (e.g., usingamplitude demodulation, phase demodulation and/or CDMA demodulation) oneor more received signals to decode an identifier associated with a NID,an ONU, a DSL modem, a tone generator, a subscribe line, a customerpremises and/or a subscriber.

To store test and/or identification results, the example loop tester 155of FIG. 7 include a loop database interface 735. The example loopdatabase interface 735 allows the loop tester 155 to store estimatedloop lengths and associated identifiers in a database (e.g., the exampleloop database 165 of FIG. 1). Database updates may be performed when aloop length and/or identifier is determined, and/or may be stored by theloop database interface 735 for subsequent storage in the database.

The example loop tester 155 of FIG. 7 is contained and/or implementedwithin a housing 740. The example housing 740 of FIG. 7 has a formfactor of a battery-powered portable and/or handheld device. However,the example housing 750 may have other form factors. For example, thehousing 750 may be a rack mountable device suitable for use and/orinstallation within a central office and/or DSLAM. Additionally oralternatively, the housing 750 may have a form factor suitable formechanical and/or electrical connection to a portable computing devicesuch as a laptop computer and/or personal digital assistant.

While an example manner of implementing any or all of the example looptesters 155 and 160 of FIG. 1 has been illustrated in FIG. 7, one ormore of the elements, processes and/or devices illustrated in FIG. 7 maybe combined, divided, re-arranged, omitted, eliminated and/orimplemented in any other way. Further, the example interface(s) 710, thecoupling circuit 715, the example power meter 720, the example looplength estimator 725, the example loop identifier 730, the example loopdatabase interface 735 and/or, more generally, the example loop tester155 of FIG. 7 may be implemented by hardware, software, firmware and/orany combination of hardware, software and/or firmware. Further still,the example loop tester 155 of FIG. 7 may include one or more elements,processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 7, and/or may include more than one of any or all ofthe illustrated elements, processes and devices.

FIG. 8 is a flowchart representative of machine accessible instructionsthat may be carried out to test one or more subscriber lines for a DSLservice using any of the example subscriber testers 155 and 160 of FIGS.1 and/or 7. The example machine accessible instructions of FIG. 8 may becarried out by a processor, a controller and/or any other suitableprocessing device. For example, the example machine accessibleinstructions of FIG. 8 may be embodied in coded instructions stored on atangible medium such as a flash memory, a ROM and/or RAM associated witha processor (e.g., the example processor 905 discussed below inconnection with FIG. 9). Alternatively, some or all of the examplemachine accessible instructions of FIG. 8 may be implemented using anycombination(s) of application specific integrated circuit(s) (ASIC(s)),programmable logic device(s) (PLD(s)), field programmable logicdevice(s) (FPLD(s)), discrete logic, hardware, firmware, etc. Also, someor all of the example machine accessible instructions of FIG. 8 may beimplemented manually or as any combination of any of the foregoingtechniques, for example, any combination of firmware, software, discretelogic and/or hardware. Further, although the example operations of FIG.8 are described with reference to the flowchart of FIG. 8, persons ofordinary skill in the art will readily appreciate that many othermethods of implementing the operations of FIG. 8 may be employed. Forexample, the order of execution of the blocks may be changed, and/or oneor more of the blocks described may be changed, eliminated, sub-divided,or combined. Additionally, persons of ordinary skill in the art willappreciate that any or all of the example machine accessibleinstructions of FIG. 8 may be carried out sequentially and/or carriedout in parallel by, for example, separate processing threads,processors, devices, discrete logic, circuits, etc.

The example machine accessible instructions of FIG. 8 begin with a looptester (e.g., the power meter 720 of FIG. 7) measuring the receivedsignal level of a received signal (block 805). The loop tester (e.g.,the example loop length estimator 725) then estimates the length of thesubscriber line on which the signal was received (block 810). The looptester (e.g., the example loop identifier 730) then demodulates thereceived signal to obtain an identifier used to modulate the receivedsignal (block 815). Next, the loop tester (e.g., the example loopdatabase interface 735) stores the estimate loop length and anydetermined identifier in a database (e.g., the example database 170 ofFIG. 1) and/or within the loop tester for later storage in the database(block 820). If more subscriber loops are to be tested and/or identified(block 820), the loop tester (e.g., the example controller 705) directsa switch (e.g., the example switch 165) to couple the next subscriberline to the loop tester (block 830). Control then returns to block 805to measure a received signal level on the next subscriber line. If nomore subscriber lines are to be tested and/or identified (block 820),control exits from the example machine accessible instructions of FIG.8.

FIG. 9 is a schematic diagram of an example processor platform 900 thatmay be used and/or programmed to implement any portion(s) and/or all ofthe example tone generator 150 and/or 525 of FIGS. 1, 4 and/or 5, and/orthe example loop testers 155 and 160 of FIGS. 1 and/or 7. For example,the processor platform 900 can be implemented by one or more processors,processor cores, microcontrollers, DSPs, DSP cores, ARM processors, ARMcores, etc.

The processor platform 900 of the example of FIG. 9 includes at leastone programmable processor 905. The processor 905 executes codedinstructions 910 and/or 912 present in main memory of the processor 905(e.g., within a RAM 915 and/or a ROM 920). The processor 905 may be anytype of processing unit, such as a processor core, a processor and/or amicrocontroller. The processor 905 may execute, among other things, theexample machine accessible instructions of FIG. 8 to implement any orall of the example loop testers described herein. The processor 905 isin communication with the main memory (including a ROM 920 and/or theRAM 915) via a bus 925. The RAM 915 may be implemented by DRAM, SDRAM,and/or any other type of RAM device, and ROM may be implemented by flashmemory and/or any other desired type of memory device. Access to thememory 915 and 920 may be controlled by a memory controller (not shown).

The processor platform 900 also includes an interface circuit 930. Theinterface circuit 930 may be implemented by any type of interfacestandard, such as a USB interface, a Bluetooth interface, an externalmemory interface, serial port, general purpose input/output, etc. One ormore input devices 935 and one or more output devices 940 are connectedto the interface circuit 930. The input devices 935 and/or outputdevices 940 may be used to implement the loop database interface 735 ofFIG. 7.

Of course, persons of ordinary skill in the art will recognize that theorder, size, and proportions of the memory illustrated in the examplesystems may vary. Additionally, although this patent discloses examplesystems including, among other components, software or firmware executedon hardware, it will be noted that such systems are merely illustrativeand should not be considered as limiting. For example, it iscontemplated that any or all of these hardware and software componentscould be embodied exclusively in hardware, exclusively in software,exclusively in firmware or in some combination of hardware, firmwareand/or software. Accordingly, persons of ordinary skill in the art willreadily appreciate that the above described examples are not the onlyway to implement such systems.

At least some of the above described example methods and/or apparatusare implemented by one or more software and/or firmware programs runningon a computer processor. However, dedicated hardware implementationsincluding, but not limited to, an ASIC, programmable logic arrays andother hardware devices can likewise be constructed to implement some orall of the example methods and/or apparatus described herein, either inwhole or in part. Furthermore, alternative software implementationsincluding, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the examplemethods and/or apparatus described herein.

It should also be noted that the example software and/or firmwareimplementations described herein are optionally stored on a tangiblestorage medium, such as: a magnetic medium (e.g., a disk or tape); amagneto-optical or optical medium such as a disk; or a solid statemedium such as a memory card or other package that houses one or moreread-only (non-volatile) memories, random access memories, or otherre-writable (volatile) memories; or a signal containing computerinstructions. A digital file attachment to e-mail or otherself-contained information archive or set of archives is considered adistribution medium equivalent to a tangible storage medium.Accordingly, the example software and/or firmware described herein canbe stored on a tangible storage medium or distribution medium such asthose described above or equivalents and successor media.

To the extent the above specification describes example components andfunctions with reference to particular devices, standards and/orprotocols, it is understood that the teachings of the invention are notlimited to such devices, standards and/or protocols. Such systems areperiodically superseded by faster or more efficient systems having thesame general purpose. Accordingly, replacement devices, standards and/orprotocols having the same general functions are equivalents which areintended to be included within the scope of the accompanying claims.

Although certain example methods, apparatus and articles of manufacturehave been described herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe appended claims either literally or under the doctrine ofequivalents.

1. A network interface device comprising: a memory storing machinereadable instructions; a processor to execute the instructions to:transmit a tone having a first amplitude based on an identifierassociated with a tone generator on a subscriber line to characterizethe subscriber line while a digital subscriber line modem is providing aservice via the subscriber line, the tone having a frequency occurringwithin a range of frequencies in use by the digital subscriber linemodem to provide the service, the tone transmitted with a signal powerlevel lower than a power associated with the service, and the toneencoded by the tone generator in the network interface to identify asubscriber and the digital subscriber line modem associated with thenetwork interface device; and a pair of terminals to communicativelycouple the digital subscriber line modem and the processor to thesubscriber line.
 2. A network interface device as defined in claim 1,further comprising a balun to match an output impedance of the tonegenerator with an impedance of the subscriber line.
 3. A networkinterface device as defined in claim 1, wherein the identification isperformed at an intermediate point of the subscriber line.
 4. A networkinterface device as defined in claim 1, wherein the tone has a signallevel selected to reduce interference with the digital subscriber linemodem.
 5. A network interface device as defined in claim 1, wherein thetone is a first tone having a first frequency, the tone generator is totransmit a second tone on the subscriber line, the second tone having asecond frequency occurring within the range of frequencies in use by thedigital subscriber line modem to provide the service.
 6. A networkinterface device as defined in claim 1, wherein the processor is tocontrol: a signal generator to generate the tone; and a modulator tomodulate the generated tone with an identifier.
 7. A loop testercomprising: a memory storing machine readable instructions; and aprocessor to execute the instructions to: measure a power of a tonereceived on a subscriber line, the tone having a first amplitude basedon an identifier associated with a tone generator and a frequencyoccurring within a range of frequencies in use by a digital subscriberline modem to provide a service via the subscriber line; verify thepower level of the tone is lower than a power associated with theservice; demodulate the received tone to identify a subscriber and thedigital subscriber line modem associated with a network interface devicebased on the received tone encoded by the tone generator in the networkinterface device; and estimate a length of the subscriber line based onthe measured power.
 8. A loop tester as defined in claim 7, wherein theprocessor is to measure a second power of a second tone received on thesubscriber line while the digital subscriber line modem is providing theservice, and to estimate the length based on the measured power and thesecond measured power.
 9. A loop tester as defined in claim 7, furthercomprising an antenna to communicatively couple the subscriber line to apower meter.
 10. A loop tester as defined in claim 7, further comprisingan optical-to-electrical converter to communicatively couple thesubscriber line to a power meter.
 11. A method to identify a subscriberloop, the method comprising: analyzing a tone having a first amplitudebased on an identifier associated with a tone generator and a frequencyoccurring within a range of frequencies in use by a digital subscriberline modem to provide a service via the digital subscriber line, thetone transmitted by the tone generator located at a network interfacedevice, wherein the tone generator is distinct from the digitalsubscriber line modem; verifying a signal power of the tone is lowerthan a power associated with the service; and demodulating the toneencoded by the tone generator to obtain a subscriber loop identifier andto identify a subscriber and the digital subscriber line modemassociated with the network interface device.
 12. A method as defined inclaim 11, wherein the analyzed tone is at least one of amplitudemodulated, phase modulated, or code-division multiple-access modulated.13. A method as defined in claim 11, further comprising estimating alength of the subscriber line based on the received analyzed tone.
 14. Amethod as defined in claim 13, wherein estimating a length of thesubscriber line based on the received tone comprises: measuring a powerof the tone; and estimating the length of the subscriber line based onthe measured power.
 15. A method as defined in claim 14, furthercomprising: measuring a second power of a second tone received on thedigital subscriber line while the digital subscriber line modem isproviding the service; and estimating the length based on the measuredpower and the second measured power.
 16. A tangible machine readablestorage medium comprising instructions which, when executed, cause amachine to perform operations comprising: accessing a tone having afirst amplitude based on an identifier associated with a tone generatorand a frequency occurring within a range of frequencies in use by adigital subscriber line modem to provide a service via the digitalsubscriber line, the tone transmitted by the tone generator located at anetwork interface device, wherein the tone generator is distinct fromthe digital subscriber line modem; verifying a signal power of the toneis lower than a power associated with the service; and demodulating thetone encoded by the tone generator to obtain a subscriber loopidentifier to identify a subscriber and the digital subscriber linemodem associated with the network interface device.
 17. A tangiblemachine readable storage medium as defined in claim 16, wherein theinstructions, when executed, cause the machine to estimate a length ofthe subscriber line based on the tone.
 18. A tangible machine readablestorage medium as defined in claim 17, wherein the instructions, whenexecuted, cause the machine to estimate a length of the digitalsubscriber line based on the received tone by: measuring a power of thetone; and estimating the length of the digital subscriber line based onthe measured power.
 19. A tangible machine readable storage medium asdefined in claim 18, wherein the instructions, when executed, cause themachine to: measure a second power of a second tone received on thedigital subscriber line while the digital subscriber line modem isproviding the service; and estimate the length based on the measuredpower and the second measured power.